Steam groups

Sure.

http://steamcommunity.com/groups/chipsandcola

http://steamcommunity.com/groups/ToFuSquad

http://steamcommunity.com/groups/redditpd

http://steamcommunity.com/groups/techjawa

http://steamcommunity.com/groups/steamgifts

Those are the ones I know of that do giveaways every so often.

Just be careful in joining a group and remember that many of them have rules of their own. If you break these rules they have every right to deny your win in a giveaway or kick you out of the group.

http://steamcommunity.com/groups/techjawa

You could always join my group that's short of members: http://steamcommunity.com/groups/peoplewholikegames

I have an group, not too many giveaways but they happen. Here there is though an F.3.A.R Giveaway going on right now!

The Realm of the Bearded Beard has a Steam group for our stream, we've had a few giveaways and we also do some for those who are site regulars (sadly a lot of people join the group without understanding that to be elligible for most of the giveaways you need to actually be part of the active community).